Lewis structures were one of the first ways developed to express chemical structure in a graphical form. In it, valence electrons are represented as dots around a central atom, depicted as its elemental symbol. For example, hydrogen has a single electron in its 1s orbital. {TODO: img} Lewis structures do not reflect molecular geometry, so the location of the dots aren’t meaningful. Fill the dots on the edges of an imaginary square around the element symbol, putting no more than two dots to a side. {TODO: img elements with dots} Two atoms can “co-own” a pair of electrons in order to fill their valence shell (see octet rule). We call this sharing arrangement a covalent bond because the electrons are considered to be in the valence shell of both atoms. {TODO: img elements with dots}
Here’s a fun toy for learning Lewis structures